1. Technical Field
The disclosure relates to a flat speaker apparatus with a heat dissipating structure and a heat dissipation method adopting the same.
2. Background
Vision and hearing are two humanity's most direct sensory responses. Therefore, scientists have been dedicated to develop various renewable visual and auditory related systems. Regarding the speakers, moving coil speakers dominate the entire market. In recent years, with people's increasing demands for sensing quality, and development trends of 3C products (computer, communication, consumer electronics) for lightness, slimness, shortness and smallness, a power-saving, light and slim speaker designed according to an ergonomic requirement is developed. Such speaker can be used in either large-size flat speakers or small walkman headphones and stereo mobile phones, and in a foreseeable future, such technology has large demand and application development.
Electroacoustic speakers are mainly grouped into direct and indirect radiation speakers, and the speakers are approximately grouped into moving coil, piezoelectric and electrostatic speakers according to driving methods thereof. The moving coil speaker is currently the most commonly used and most mature product. However, a moving coil speaker cannot be compressed due to the physical structure thereof. Accordingly, moving coil speaker is not suitable for 3C products and home entertainment systems which have their sizes reduced constantly.
In the piezoelectric speaker, an electric field is applied to the piezoelectric material to cause deformation according to a piezoelectric effect of a piezoelectric material, so as to drive a vibrating membrane to generate sound. Although such speaker has a flat and miniaturized structure, the sound quality thereof is limited.
Main products of the electrostatic speaker in the market include hi-end earphones and loudspeakers. A functional principle of the conventional electrostatic speaker is to use two fixed porous electrode plates to clamp a conductive vibrating membrane to form a capacitor, and by supplying a direct current (DC) bias to the vibrating membrane and supplying an alternating current (AC) voltage to the two fixed electrodes, the conductive vibrating membrane is vibrated due to an electrostatic force generated under a positive and a negative electric fields, so as to radiate a sound. The bias of the conventional electrostatic speaker has to reach hundreds to thousands voltages, so that an external amplifier with a high price and a great size has to be applied, and therefore application thereof cannot be widespread.
In addition, according to the conventional techniques, during a mass production, speaker units have to be produced individually, and the speaker generally has a fixed size or shape, so that effective mass production and cost reduction cannot be achieved, and features of softness, thinness, low driving voltage and flexibility of the speaker cannot be achieved.
Moreover, driving circuit modules of the moving coil, piezoelectric, or electrostatic speakers all have large volume and heavy weight, and usually occupy certain amount of space and weight. The volumes and weight mostly come from heat dissipating structures of the driving circuit modules.
Since the flat speaker requires a high voltage, high current, and high power driving method to achieve larger volume and better frequency response curve, electronic devices within the driving circuit module then eventually generate high heat. In order to prevent high heat, temperature sensors, heat sinks, and fans are conventionally adopted for heat dissipation so as to ensure the proper functioning of the system. However, lightness, softness, thinness, flexibility, and low driving voltage are the major requirements of flat speakers, and the disposition of temperature sensors, heat sinks, and fans is contrary to these requirements. Furthermore, fans generate interfering current and noise, thereby affecting the operation of flat speakers and the sound quality perceived by the user. Additionally, about 35% of the circuit board space and 20% of the component costs can be saved if the heat sinks, the temperature sensors, controllers, and enabling switches are removed effectively.